Checkbox/X icon bad height when itemHeight is used. (and some misc feedback)

[jorgemmsilva]

First of all, thanks for the work on this library - the component is quite cool.

Expected Behavior

Checkboxes and "remove icons" should resize according to itemHeight prop.

Actual Behavior

Checkboxes do not obey the itemHeight value - leading to wrong selections when clicked.
(the same applies to the 'x' icon on the selected items)
This is fixable by css with something like this:

  div[aria-label="grid"]>div {
    div>div>span {
      height: 20px;
    }
  }

But it's an hack. The lib should handle this.

Steps to Reproduce the Problem

1. set the itemHeight prop to something less than 40px

Other feedback:

• better styles customisation - allow custom classes for listItems (or even better use https://emotion.sh/ )
• allow a selector for the Id of each item (which imo should be called value) - having a getId prop that receives a function

Neat Features:

• "Select/Deselect All" checkbox for each group

^ I might create a PR for some of that in the future if I get the time :)